'Expanse' in the Bible

Over the head of the living creature there was the likeness of an expanse, like the awesome crystal to look on, stretched forth over their heads above.

Under the expanse were their wings straight, the one toward the other: each one had two which covered on this side, and every one had two which covered on that side, their bodies.

There was a voice above the expanse that was over their heads: when they stood, they let down their wings.

Above the expanse that was over their heads was the likeness of a throne, as the appearance of a sapphire stone; and on the likeness of the throne was a likeness as the appearance of a man on it above.

Then I looked, and see, in the expanse that was over the head of the cherubim there appeared above them as it were a sapphire stone, as the appearance of the likeness of a throne.